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| 2. |
- Hepojoki, J, et al.
(författare)
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Acute hantavirus infection induces galectin-3-binding protein
- 2014
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Ingår i: The Journal of general virology. - : Microbiology Society. - 1465-2099 .- 0022-1317. ; 95:Pt 11, s. 2356-2364
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Tidskriftsartikel (refereegranskat)abstract
- Hantaviruses are zoonotic viruses that cause life-threatening diseases when transmitted to humans. Severe hantavirus infection is manifested by impairment of renal function, pulmonary oedema and capillary leakage. Both innate and adaptive immune responses contribute to the pathogenesis, but the underlying mechanisms are not fully understood. Here, we showed that galectin-3-binding protein (Gal-3BP) was upregulated as a result of hantavirus infection bothin vitroandin vivo. Gal-3BP is a secreted glycoprotein found in human serum, and increased Gal-3BP levels have been reported in chronic viral infections and in several types of cancer. Ourin vitroexperiments showed that, whilst Vero E6 cells (an African green monkey kidney cell line) constitutively expressed and secreted Gal-3BP, this protein was detected in primary human cells only as a result of hantavirus infection. Analysis of Gal-3BP levels in serum samples of cynomolgus macaques infected experimentally with hantavirus indicated that hantavirus infection induced Gal-3BP alsoin vivo. Finally, analysis of plasma samples collected from patients hospitalized because of acute hantavirus infection showed higher Gal-3BP levels during the acute than the convalescent phase. Furthermore, the Gal-3BP levels in patients with haemorrhagic fever with renal syndrome correlated with increased complement activation and with clinical variables reflecting the severity of acute hantavirus infection.
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| 3. |
- Meri, T, et al.
(författare)
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Relapsing fever Spirochetes Borrelia recurrentis and B. duttonii acquire complement regulators C4b-binding protein and factor H
- 2006
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Ingår i: Infection and Immunity. - 1098-5522. ; 74:7, s. 4157-4163
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Tidskriftsartikel (refereegranskat)abstract
- Relapsing fever is a rapidly progressive and severe septic disease caused by certain Borrelia spirochetes. The disease is divided into two forms, i.e., epidemic relapsing fever, caused by Borrelia recurrentis and transmitted by lice, and the endemic form, caused by several Borrelia species, such as B. duttonii, and transmitted by soft-bodied ticks. The spirochetes enter the bloodstream by the vector bite and live persistently in plasma even after the development of specific antibodies. This leads to fever relapses and high mortality and clearly indicates that the Borrelia organisms utilize effective immune evasion strategies. In this study, we show that the epidemic relapsing fever pathogen B. recurrentis and an endemic relapsing fever pathogen, B. duttonii, are serum resistant, i.e., resistant to complement in vitro. They acquire the host alternative complement pathway regulator factor H on their surfaces in a similar way to that of the less serum-resistant Lyme disease pathogen, B. burgdorferi sensu stricto. More importantly, the relapsing fever spirochetes specifically bind host C4b-binding protein, a major regulator of the antibody-mediated classical complement pathway. Both complement regulators retained their functional activities when bound to the surfaces of the spirochetes. In conclusion, this is the first report of complement evasion by Borrelia recurrentis and B. duttonii and the first report showing capture of C4b-binding protein by spirochetes.
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| 4. |
- Meri, T, et al.
(författare)
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The hyphal and yeast forms of Candida albicans bind the complement regulator C4b-binding
- 2004
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Ingår i: Infection and Immunity. - 1098-5522. ; 72:11, s. 6633-6641
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Tidskriftsartikel (refereegranskat)abstract
- Candida albicans, an important pathogenic yeast, activates all three pathways of the complement system. To understand how this yeast evades the effects of the activated system, we have analyzed the binding of the classical pathway inhibitor C4b-binding protein (C4BP) by C. albicans. Purified native as well as recombinant C4BP bound dose dependently to the yeast and hyphal forms, as shown by multiple methods, such as confocal microscopy, flow cytometry, a novel enzyme-linked immunosorbent assay, absorption from human serum, and direct binding assays with purified proteins. A prominent binding site was identified at the tip of the germ tube, a structure that is considered important for tissue penetration and pathogenesis. The binding site in C4BP was localized to the two N-terminal complement control protein domains by using recombinant deletion constructs and site-specific monoclonal antibodies. As the alternative pathway inhibitors factor H and FHL-1 also bind to C. albicans, the binding of all three plasma proteins was compared. Simultaneous binding of the classical regulator C4BP and the alternative pathway regulator factor H was demonstrated by confocal microscopy. In addition, FHL-1 competed for binding with C4BP, suggesting that these two related complement regulators bind to the same structures on the yeast surface. The surface-attached C4BP maintains its complement regulatory activities and inactivates C4b. The surface-attached human C4BP serves multiple functions relevant for immune evasion and likely pathogenicity. It inhibits complement activation at the yeast surface and, in addition, mediates adhesion of C. albicans to host endothelial cells.
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| 7. |
- Eichner, Meri, et al.
(författare)
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Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO2
- 2017
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Ingår i: ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 11, s. 1305-1317
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 The Author(s)Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2 were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2 concentrations over a day–night cycle. O2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2 (up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15nmoll-1 proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2 levels, whereas N2 fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments.The ISME Journal advance online publication, 11 April 2017; doi:10.1038/ismej.2017.15.
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| 8. |
- Holmberg, Mikko T., et al.
(författare)
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Regulation of complement classical pathway by association of C4b-binding protein to the surfaces of SK-OV-3 and caov-3 ovarian adenocarcinoma cells
- 2001
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Ingår i: Journal of Immunology. - 1550-6606. ; 167:2, s. 935-939
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Tidskriftsartikel (refereegranskat)abstract
- The role of fluid-phase regulators of complement is to inhibit excessive complement activation and maintain homeostasis in blood. By binding to and inactivating complement components on cell surfaces, they can also protect autologous cells from complement-mediated cytotoxicity and phagocytosis. In this study, we wanted to find out whether C4b-binding protein (C4bp), a fluid-phase regulator of the classical complement pathway, could directly bind to cell surfaces in a functionally active form. After screening several malignant cell lines, we observed that the ovarian adenocarcinoma cell lines SK-OV-3, Caov-3, and SW626 were capable of binding C4bp. Binding tests with recombinant deletion mutants suggested that the primary binding site on C4bp is located on the alpha -chain complement control protein 4 domain. Functional tests showed that tumor cell-bound C4bp retained its cofactor activity for factor I-mediated inactivation of CO, thus increasing the control of classical complement pathway activation on the surfaces of these cells. These results demonstrate a novel mechanism of complement regulation on cell surfaces, particularly on those of malignant ovarian tumor cells.
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| 9. |
- Jokiranta, T S, et al.
(författare)
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Complement C3b interactions studied with surface plasmon resonance technique
- 2001
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Ingår i: International Immunopharmacology. - 1567-5769 .- 1878-1705. ; 1:3, s. 495-506
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Tidskriftsartikel (refereegranskat)abstract
- The surface plasmon resonance (SPR) phenomenon is utilized in a number of new real time biosensors. In this study, we have used this technique to study interactions between the central complement component C3b and its multiple ligands by using the Biacore equipment. The SPR technique is particularly suitable for analysis of the alternative complement pathway (AP) because the inherent nature of the latter is to amplify deposition of C3b on various surfaces. C3b was coupled onto the sensor surface and the coupling efficiency was compared under various conditions on both polystyrene and carboxymethylated dextran surfaces. After enzymatic C3b coupling or standard amine C3b coupling, we analyzed and compared the binding of four C3b ligands to the surface: factor B, factor H, C5 and the soluble complement receptor 1 (sCR1, CD35). Binding of each ligand to C3b was detected when C3b had been coupled either enzymatically or using the amine coupling, but the half-lives of the interactions were found to vary depending on the coupling procedure. Factor H binds to C3b via three interaction sites. The target sites are exposed on the C3b, C3c and C3d fragments of C3, respectively. Therefore, we also tested by using the Biacore whether factor B, C5 and sCR1 bind to C3c and/or C3d. It was found that factor B bound to C3d, but not to C3c. On the other hand, both C5 and sCR1 bound to C3c, but not to C3d. In conclusion, this study shows that SPR is a powerful tool in analyzing and mapping the interactions of C3b with its multiple ligands.
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